1. Field of the Invention
The present invention is concerned with ways of increasing the efficiency of fastening materials together with screw fasteners and is especially concerned with increasing the efficiency and convenience of accomplishing the fastening in areas where close tolerances are required, such as in cabinetmaking. A further object of the invention is to eliminate many separate tool-handling steps in such fastening operations which previously required a separate tool for drilling, counterboring, countersinking and for securing the screw fastener in place. Other areas in which the present invention is useful are in situations where the user is required to fasten things with screw means from a ladder, scaffold or the like where there is no convenient rest for power tools such as drills, screw drivers and the like. The present invention provides a combination tool which eliminates many of the handling steps previously required in such operations. The present invention also incorporates built-in guides for controlling the depth of bores, countersinks and counterbores.
2. Prior Art
There are no known references suggesting or closely related to the combination tools disclosed and claimed herein. A few attempts in the past have been made to combine drilling and screwdriving operations but they have not been perfected to any extent.
In U.S. Pat. No. 3,869,741 Logan, there is disclosed a screwdriver bit for a Phillips-head screwdriver which has a threaded portion behind the screw engaging end of the screwdriver which serves to ream out pre-drilled holes such as in painted sheet metal wherein the paint may have clogged the prepunched holes which require unclogging due to the presence of paint.
U.S. Pat. No. 3,207,196 Stillwagon, Jr. discloses a countersinking tool which is in the form of a screwdriver bit for a Phillips-head type of screwdriver extend outwardly in two tapering steps in order to provide countersinking and counterboring effect due to a wearing or rubbing through the abrasion of the tool by its wings upon soft wall board or like material. This tool is not a cutting tool but merely a brading tool and does not suggest any way to actually cut or bore the hole or to cut out a countersink. Furthermore, there is no positive control on the depth of the countersink or counterbore which might be formed by the tool. Hence, it is totally unsuitable for precision operations.
The present invention provides a combination tool for use in screw fastening of materials together wherein convenience, efficiency and precision are of great importance, for example, in such areas as kitchen cabinetmaking. The tool of the present invention combines in one tool a screwdriver and drill not only for boring pilot holes for screws but providing counterboring and countersinking operations.
This is accomplished through two general embodiments of the invention.
In the first embodiment, the screwdriver-drill bit combination incorporating the present invention is adapted to be secured to the distal end of any standard drill by way of magnetic fastening, set screws, chucks or the like. The distal end of the bit in this first embodiment of the invention is shaped in the form of a Phillips-head screwdriver or the like with wings at right angles to each other with flutes or valleys in between. At the distal end, the wings are tapered upwardly in the form of the usual Phillips-head type of screwdriver or the like. Behind this taper, the wings thereafter are parallel to the longitudinal axis of the bit for a distance which is determined by the desired width and depth to be utilized in the bit. Optionally, they can blend in with the cylindrical shaft of the bit. In various modifications of the type of bit, the wings can taper outwardly further following the above boring section to form a countersinking cut at the angle desired and then become parallel to the longitudinal axis or merge into outer cylindrical surface of the bit. The proximal end of the bit is provided with a suitable fastening means to the tool drive and in most cases, as in a cabinetmaking type of tool, a standard magnetic holding means is employed.
In the preferred form of this embodiment, the shaft of the tool at the upper portion thereof is provided with a series of annular grooves to provide securing means for an annular collar from the lower portion of which collar is a depending skirt. The skirt serves to control the depth of the countersink, and the skirt is provided with transverse openings through which shavings can be dispersed.
There are various modifications in the shape and slope of the wings that may be utilized within the scope of the present invention. The wings involved are provided with hardened and sharpened edges to cut on the outer edge of the face of the wing on the side in the direction of the normal rotation of the drill. This, for most operations, is more than adequate cutting means.
In a further embodiment of the invention, the bit for the screwdriver is provided with a longitudinal central passage therein through which a drill bit retractably passes. A drill bit of a suitable length is secured to the driving source of the tool. A cylindrical shaft having a hollow central portion through which the bit passes in close but non-engaging tolerance is passed over the bit and secured to the bit so that they rotate together when the shaft is driven. It is secured by means of a normal set screw which is tightened against the drill bit.
The outer shaft is provided with diametrically opposed pins extending from its sides which serve to lock the shaft into longitudinally sliding engagement with an outer cylindrical shell casing normally riding longitudinally in corresponding longitudinal grooves in the internal surfaces of the outer shell casing. In one modification, however, the pins on the shaft are secured in diametrical slots in the walls of said casing at the distal end of the casing relative to the operative end of the tool. An internal central passage of the outer shell casing is provided with an annular shoulder at the upper portion thereof in order to retain a coil spring which is located about the shaft and between the shoulder and a ring lock adjacent the base of the shaft.
Between this ring and the lower portion of the shaft is another coil spring of somewhat greater tension than the upper spring which surrounds the drill bit and extends to the distal end of the lower portion of the shaft. Adjacent the lower end of the outer shell, the drill bit passes through a cylindrical guide block having a central passage therethrough which guide block is locked in place by retaining springs set into circumferential grooves in the lower portion of the outer shell. The cross section of the outer shell in its lowermost regions is non-circular so that the screwdriver bit may be locked in place relative to rotation of the outer shell.
In operation, the downward pressure by the operator forces the end of the drill bit through the central opening of the screwdriver bit to perform normal drilling operations and the screwdriver bit merely serves as a guide for locating the bit. When it is desired to utilize the screwdriver function, the outer shell is pulled down and turned one-quarter turn to lock the diametrical pins of the inner shaft into slots in the upper portion of the outer shell casing, which in turn prevents the sliding longitudinal movement of the device's drill bit relative to the outer shell and screwdriver bit.